Magnetic transfer method refers to all action related to the movement of particles by means of magnetism, such as assorting, collecting, transferring, mixing and dosing within a solution or from one solution to another.
Particles, microparticles or magnetic particles refer to all such small particles that have their diameter in the range of micrometers, and that can be moved by means of magnetism. There are various known particles that are transferable with a magnet and applications, where they are used, also greatly vary. For example, particles used in microbiology usually have a size of 0.01-100 μm, most commonly 0.05-10 μm. Such known particles are, for example, particles containing ferromagnetic, paramagnetic or supramagnetic material. Particles can also be magnetic themselves, whereby they can be moved by means of any ferromagnetic object.
In a device intended to treat microparticles, there is a unit exploiting magnetism, that is hereinafter referred to as a magnet. It can be a permanent magnet or an electrical magnet, that attracts ferromagnetic particles, or a ferromagnetic object, that is not magnetic itself, but still attracts magnetic particles.
A magnet is usually preferably a rounded bar magnet. It can also be a bar of another shape. However, a magnet does not need to be a bar at all. It can also be short and broad or an object of any shape. A magnet can also consist of one or more objects, such as magnets or ferromagnetic objects.
There has to be a shield covering the magnet, protecting the magnet from various harmful conditions and enabling the treatment of microparticles, such as binding and release. The structure of the shield may greatly vary, for it can be, for example, a thin membrane made of flexible or stretching material or even a cup made of rigid plastic.
Microparticles are usually used as the solid phase to bind various biomolecules, cell organelles, bacteria or cells. For example, enzymes can be immobilised on the surface of microparticles, whereby the treatment and further use of the enzymes is efficient. Most of the so called magnetic nanoparticles (<50 nm) are not suitable to be treated with regular permanent magnets or electrical magnets, but require the use of an particularly strong magnetic gradient, as described in EP 0842704 (Miltenyi Biotec). Magnetic particles, such as microparticles, that have a diameter of about 0.1 pm or more, can usually be treated with regular permanent or electrical magnets. The viscosity of the solution can also considerably hamper the picking of the particles. The particles to be picked can be originally suspended in the solution, where a substance is desired to be bound, or, say, cells on the surface of the microparticles.